Extraction of tensile properties of metallic alloys by small punch test: benchmarking inverse finite element method versus empirical correlations

The miniaturized specimens of three metallic alloys (bainitic reactor pressure vessel steel, ferritic-martensitic steel Eurofer97 and fcc CuCrZr alloy) important for nuclear and fusion applications are subjected to the small punch tests (SPTs) at room and elevated (300°C) temperatures. The baseline plasticity metric, such as yield stress, is extracted from the SPT results by means of various empirical and FEM-assisted correlations and inverse finite element method (IFEM) simulations. Further strain hardening data (up to 10 % plastic strain) is also extracted from the SPT results by the IFEM. Later on, the accuracy of the derived yield stress and strain hardening behavior is compared with the reference results of the uniaxial tensile tests.
For both studied temperatures the IFEM calculations were proven to show the best overall accuracy for the extraction of the yield stress for all the studied materials. As a simplified alternative, the FEM-assisted single-value empirical correlation based on the method from the European EN standard can be recommended for the extraction of the yield stress from RPV steels. The extraction of strain hardening behavior up to 5 % plastic strain from SPTs at both test temperatures was found to be consistently feasible only for softer alloys such as CuCrZr.